When it comes to choosing a solar charge controller for a photovoltaic system, two main technologies are often compared: PWM (Pulse Width Modulation) charge controllers and MPPT (Maximum Power Point Tracking) charge controllers. Each of these technologies has its own characteristics, advantages and disadvantages, which can influence the choice according to the specific needs of the system.
PWM controller: simplicity and cost
PWM controllers are often chosen for their simplicity of design and generally lower cost. Their operation is based on a direct connection between the solar panel and the battery, which means that the battery voltage determines the operating voltage of the solar panel. For example, a solar panel producing 120W with an optimum operating voltage (UMPP) of 17V and a current of 7A, connected to a 12V battery via a PWM regulator, will only deliver 84W (12V x 7A) to the battery, well below its maximum capacity of 120W.
The reason for this limitation is that the PWM regulator cannot adjust the panel voltage to match the maximum power point (PMPP) of the solar panel. As a result, a significant part of the panel's potential energy is lost, which can represent a loss of 15 to 35% on average. However, for small or simple systems, where budget is a major constraint and energy efficiency requirements are less stringent, a PWM controller may be a reasonable choice.
MPPT controller: efficiency and performance
In contrast, MPPT controllers offer far superior performance by maximizing the energy captured by solar panels. They work by analyzing the solar panel's power curve in real time to identify the Maximum Power Point (MPP). This point represents the optimum combination of voltage and current (UMPP x IMPP) at which the solar panel produces its maximum power.
Once this point has been identified, the MPPT controller electronically converts the panel's optimum power into a voltage corresponding to that of the battery, while increasing the charging current. This maximizes the system's efficiency and fully utilizes the solar panel's capacity. So, in the same example where a 120W solar panel is used, an MPPT controller would exploit all the available power, i.e. all 120W, by adjusting voltage and current to match battery requirements.
Although MPPT controllers are more expensive than PWM controllers, they are particularly advantageous in larger systems, where energy efficiency is crucial, or where environmental conditions (such as variations in temperature and sunshine) strongly influence solar panel performance. Their ability to maximize energy production over a wide range of conditions makes them ideal for installations where every watt counts.
Conclusion: The choice between cost and performance
The choice between a PWM and an MPPT controller depends primarily on the priorities of the solar system in question. If the budget is limited and simplicity is the goal, the PWM controller may suffice, particularly for small systems where the loss of efficiency is tolerable. On the other hand, for systems where optimization of energy production is essential, such as larger installations or variable environments, the MPPT controller is the best option, offering a higher return on investment thanks to better utilization of the energy produced by the solar panels.